void swap(int in_1, int in_2);

int main(void)
{
    int x = 1;
    int y = 2;
    printf("x = %dn", x);
    printf("y = %dn", y);
    printf("swapping...n");
    swap(x,y);
    printf("x = %dn", x);
    printf("y = %dn", y);
}

void swap(int in_1, int in_2)
{
    int temp = in_1;
    in_1 = in_2;
    in_2 = temp;
    return;
}

void swap(int* a, int* b)
{
    int tmp = *a;
    *a = *b;
    *b = tmp;
}